There are two technical requirements in stimulating techniques applied in visual measurement methods for creating a visual response: the way the visual stimulus has been pointed to the eye and the way other factors of the stimulus source than factors of light effect have been eliminated from the object for measurement. In visual measurement methods based on recognized techniques which have been designed for measuring the physiological potential change of retina of the eye (electroretinogram, ERG) for a visual stimulus carried out on test animals has been represented that by applying mirrors, lenses or a LED-light source or a flashlight aligned to the eye the beams of the light may be pointed to the retina and to various parts of it while the subject to be examined stays on place or has by some means made immovable. (Documenta Ophthalmologica 98, 2000, Bayer A. U., Mittag T., Cook P., Brodie S. E., Podos S. M. and Maag K-P. “Comparisons of the amplitude size and the reproducibility of three different electrodes to recorded the corneal flash electroretinogram in rodents”, p. 233-246; Documenta Ophthalmalogica 81, 1992, Hawlina M. and Konec B., “New noncorneal HK-loop electrode for clinical electroretinography”, p. 253-259; U.S. Pat. No. 4,255,023; U.S. Pat. No. 5,506,633; SU-patent publication 1 648 336).
The measuring of ERG-potentials corresponding with the magnitude of visual stimulus from a laboratory animal or a human moving freely creates a technical problem because in free motion the direction of gaze in 3-dimensional space as well as the place of the body or a part of it such as the head continuously changes between different measurements. Another common technical problem while applying some visual stimulus sources, such as a flashlight, are other physical effects created by them than the changes in light intensity, which other physical effects may be the change in magnetic field and sound, among other things. The solving of the problem should effect such that the magnitude of the visual sense is independent of the direction of the gaze of the subject, the body or a part of it may not hinder the transmitting of the visual stimulus and other than light effects of the light stimulus source are excluded in the object for measuring.
The object of the invention is to eliminate these disadvantages and to provide a visual stimulator, which enables the registration of an ERG-response created by a visual stimulus as well as registration of other biopotential responses connected with other visual processes from a laboratory animal or a human moving freely and being conscious such that the direction of the gaze or the place of the body or a part of the body, such as the head, must not be constant between different measuring situations. In addition, the object of the invention is to provide a device which excludes other than light stimulating factors, which other factors might arise from the applying of the light stimulating source.